1. Field of the Invention
The present invention is directed to a lamp unit utilized in a photoirradiating-type heating device that carries out heating treatment utilizing light for growing, diffusing and annealing semiconductor wafers. More particularly, the invention is directed to lamp unit that is useful in a photoirradiating-type heating device that does not contaminate the processing chamber of the device, that permits the lamp to be reliably cooled, that permits the lamp to be reliably turned on, that inhibits the decline in the reflectance on the inner surface of an optical guide, and that permits attenuation of irradiation intensity to be inhibited. The lamp unit has a metal sleeve with an aperture at one end and a single ended lamp mounted so that sealed part of the lamp would be situated on the inside of the sleeve on the aperture side of sleeve, a coupling member having contact support unit that makes contact with the outer surface of a sealed part of the lamp by elastic force as well as a contact fastening unit that makes contact with the inner surface of the sleeve after the contact support unit and that also fastens a single ended lamp to the sleeve.
2. Description of the Related Art
Photoirradiating type heating devices have been used over a broad range of procedures in semiconductor production including growth, diffusion and annealing. Semiconductor wafers are subjected to uniform heating processing at high temperatures to rapidly heat wafers through photoirradiation in all processing, and temperature elevation to levels exceeding 1000 degrees Celsius can take anywhere from a dozen seconds to several dozen seconds. After holding at a fixed temperature, the wafer is rapidly cooled by halting photoirradiation.
FIG. 1 shows a conventional photoirradiating-type heating device as is known from U.S. Pat. No. 5,155,336. In the figure, a wafer 3 is shown supported on a wafer suppport stage 2 for heat processing within a processing chamber 1 partitioned by a quartz window 8. The quartz window 8 is used when the ambient atmospheres of the wafer 3 and the lamp 4 differ. The lamp 4 is a single ended lamp in which a sealed part 41 is mounted only at one edge of the lamp 4. As shown in FIG. 1, a plurality of lamps are disposed over the wafer 3. The sealed part 41 of each lamp 4 is disposed within cylindrical metal sleeve 5. The lamp 4 is fastened to the sleeve 5 by an adhesive and the sleeve 5 is mated within a cylindrical optical guide 7 composed of a metal-plated stainless steel that is fastened to a wall member 6. The space formed by the wall 6 and the optical guide 7 forms a cooling chamber 9 in which a cooling liquid is flowed.
As shown in FIG. 2, a front optical guide 71 is mounted in front of the aperture of the optical guide 7 to efficiently reflect light from the lamp 4 off of wafer 3, but the optical guide 7 may be extended to complete a structure that doubles as the front optical guide 71. When power is applied to the lamp 4, the filament within the lamp 4 fires and the light that is irradiated directly upon the wafer 3 is also reflected off the inside reflecting surface of front of the optical guide 71, thereby heating the wafer 3. A cooling liquid is flowed within the cooling chamber 9 so that the temperature of the sealed part 41 of the lamp 4, the optical guide 7 and the sleeve 5 is not raised excessively by the radiant energy from the lamp 4. The sealed part 41 of the lamp 4 is positioned within at one end of the cylindrical metal sleeve 5. The sealed part 41 is fastened to the sleeve 5 by an inorganic, inelastic adhesive S. In this way, a lamp unit is constructed in which lamp 4 and sleeve 5 are integrated by adhesive S. The sleeve 5 is constructed so that the sides contact cylindrical optical guide 7. Adhesive S fastens lamp 4 and also vents heat from sealed part 41 accompanying lighting of lamp 4 as well as heat from the luminous tube after sealed part 41 to sleeve 5 via adhesive S. Heat transmitted to sleeve 5 is conveyed to optical guide 7 which is cooled by the cooling liquid circulating about the exterior of optical guide 7 to ultimately cool lamp 4.
The conventional device, however, has several disadvantages. For example, adhesive S packed in sleeve 5 is exposed to processing chamber 1 at the bottom of optical guide 7. When stress is repeatedly applied to inelastic adhesive S through turning lamp 4 on/off, part of adhesive S peels off and falls into processing chamber 1 to contaminate it. In addition, when packing adhesive S within slender sleeve 5, it is difficult to completely pack adhesive S within sleeve 5, and thereby leaving gaps K where adhesive S was not packed within sleeve 5. In this case, efficient venting of heat from sealed part 41 via adhesive S is impossible due to such gaps K. Adequate cooling cannot be carried out and the cooling effect is attenuated. Furthermore, if adhesive S packed within slender sleeve 5 is inadequately dried because of the difficulty of complete drying, lead wires 10 are shorted by moisture contained within adhesive S when lamp 4 is turned on and lamp 4 becomes inoperative.
In addition, adhesive S is heated when lamp 4 is turned on and the moisture contained within adhesive S is released. It then contaminates the inner surface N (the region denoted by the broken lines for convenience) of front optical guide 71 on the aperture side of optical guide 7, thereby lowering the reflectance on the inner surface of front optical guide 71, and precluding efficient wafer heating. When lamp 4 is lit, the temperature of adhesive S rises, thereby releasing moisture contained in adhesive S. This causes devitrification of the luminous tube of lamp 4 which lowers the irradiation intensity.
Accordingly, an object of the invention is to overcome the disadvantages of the prior art in devising a lamp unit that is useful in a photoirradiating type heating device that does not contaminate the processing chamber of a photoirradiating type heating device, that permits the lamp to be reliably cooled, that permits the lamp to be reliably turned on, that inhibits the decline in the reflectance on the inner surface of an optical guide, and that permits attenuation of irradiation intensity to be inhibited.
The lamp unit includes a cylindrical metal sleeve having an aperture at one end and made of SUS steel and a single ended lamp mounted so that a sealed part of the lamp can be situated on the inside of the sleeve. The lamp is fastened to the sleeve by a coupling member attached to the sleeve and which supports the sealed part of the lamp. The coupling member is composed of a single piece of aluminum that is bent so as to form a contact support unit and a contact fastening unit. Due to the bending, elastic force is generated in the contact support units and the contact fastening units.
The contact support units contact the outer surface of the sealed part of the lamp to enable the coupling member to pinch and support the sealed part by elastic force. Accordingly, the contact fastening units that contacts the inner surface of the sleeve is formed after the contact support unit. The contact fastening unit makes contact with the inner surface of the sleeve utilizing the force that opens outwardly through the elastic stress of the coupling member itself. The contact fastening unit fits against a projection to thereby fasten the lamp to the sleeve.
In this way, the various problems associated with using an adhesive are obviated since the lamp is mechanically fastened without using an adhesive. For example, the interior of the processing chamber is not contaminated by peeling of adhesive itself and the shorting of lead lines that supply power to lamp do not occur due to the effects of moisture contained in the adhesive. Moreover, the decline in the reflectance due to the contamination by moisture on the inner surface of the optical guide or front optical guide and devitrification of the luminous tube do not occur. And, the irradiation intensity is not attenuated since adhesive is not used.
Furthermore, since the sleeve is mated to the optical guide on its outer circumferential surface, heat from the lamp is transmitted to the coupling member via the sealed part. The heat transmitted to coupling member is subsequently transmitted to the sleeve. The heat transmitted to sleeve is subsequently transmitted to the optical guide. The heat transmitted to the optical guide is subsequently transferred to the cooling liquid circulating on the outer surface. Consequently, a series of heat-conduction passages are formed that reliably cool the lamp.
The coupling member need not be composed exclusively from metal, and pre-molded plastic having a high heat resistance or a ceramic material coated on the surface with a heat-transmitting material may be used. In short, any unit that reliably fastens the lamp to the sleeve and which transmits heat from the lamp to the sleeve may be used. A heat-transfer sleeve that does not impair the support between the sealed part and the contact support unit of the coupling member and which raises the heat-transfer characteristics may be interposed to improve the contact between these units.
The section of the coupling member opposes a luminous unit of the lamp and forms a reflection surface. The reflectance on the surface of reflection surface can be raised by applying a metal coating. As a result, the light radiated from the lamp and reflected from the inner surface of the front optical guide and then returned toward the lamp can be efficiently reflected in the direction of the aperture of the front optical guide to permit efficient wafer heating.
In a second embodiment, the lamp unit includes a coupling member comprising a contact fastening unit composed of a block of aluminum and a flat contact support unit composed of copper. When the contact support unit contacts the sealed part, part of the contact support unit forms a projection which mates with a depression of the sealed part to reliably support the lamp. On the other hand, the external shape of the contact fastening unit is cylindrical, having an outer diameter which is roughly equal to the inner diameter of the sleeve. The contact fastening unit is pushed and press-fit to the forward aperture of the sleeve with the outer circumference of the contact fastening unit mated and fastened to the inner surface of the sleeve.
The contact support unit comprises a set of metal plates, one end of which is bent in advance to provide elasticity to the projection. An insertion aperture of the lamp sealed part contact fastening unit is fitted in this state. When one end of the contact support unit penetrates the contact fastening unit, the other edge that penetrates and jumps out is bent. The sealed part of the lamp is press-fit in the gap formed with the opposing contact support unit, and both sides of the sealed part are pinched and supported by the contact fastening unit. The surface of the contact support unit that faces the luminous unit of the lamp then forms the reflection surface.
In a third embodiment, the lamp unit includes a coupling member having a contact support unit and the contact fastening unit as separate units. The contact support unit comprises a set of metal plates that are bent in prescribed shape, to provide elasticity. The plates contact both sides of the sealed part to pinch and support it. While the lamp is supported by the contact support unit, it is fitted so as to contact the inner surface of the contact fastening unit. Accordingly, contact support unit is firmly fastened to the contact fastening unit by the outward expansive elastic force of the contact support unit and the sealed part is pinched and supported by the contact support unit.